It is probably a coincidence that the three main terms discussed in this book, namely transformations, projections,and perspective, are ambiguous. Here is what the dict- nary has to say about these terms. Transformation (a) The act or an instance of transforming. (b) The state of being transformed. A marked change, as in appearance or character, usually for the better. Mathematical transformation. (a) Replacing a variable in an expression by its value. (b) Mapping a mathematical space onto another or onto itself. In geometry. Moving, rotating, re?ecting, or otherwise systematically deforming a geometric ?gure (discussed in this book). In linguistics. (a) A rule to convert a syntactic form into another. (b) A sentence or sentential form derived by such a rule; a transform. In genetics. (a) The change undergone by a cell upon infection by a cancer-causing virus. (b) The alteration of a bacterial cell caused by the transfer of DNA from another bacterial cell, especially a pathogen. Projection The act of projecting or the condition of being projected. (a) An object or part thereof that extends outward. (b) Spiky projections on top of a fence. (c) A projection of land along the coast. A prediction or an estimate of a future situation, based on current data or trends. (a) The process of projecting a recorded image onto a viewing surface. (b) An image so projected.